Catalytic igniter for ram-jet burner



Feb. 7, 1961 w. G. BERL 2,970,439

CATALYTIC IGNITER FOR RAM-JET BURNER Filed Sept. 15, 1949 FIG! 28 INVENTOR.

WALTER G. BERL ATTORNEY CATALYTIC IGNITER FOR RAM-JET BURNER Filed Sept. 13, 1949, Ser. No. 115,368

6 Claims. (Cl. 60-3932) The present invention relates generally to an igniter for use in guided missiles.

More specifically, the invention relates to an improved igniter for use in the burner assembly of a ram-jet engine, or athodyd.

In order to attain smooth and eflicient burning in the combustion chamber of a ram-jet engine, it is highly important that proper ignition of the homogeneous air-fuel mixture passing through the chamber take place. This is attained by providing a minimum amount of heat to the air-fuel mixture. Because the amount of heat required varies with the type of fuel being burned, and because some fuels require a longer ignition period, or possibly a continuous pilot flame, a simple igniter having a widely variable rate of heat exchange, in addition to long life, is desirable.

Known igniters having the characteristics set forth above have proven to be unduly large and complex, requiring special apparatus to provide initial ignition of the pilot flame itself, as well as control over the rate of heat exchange. Simple igniters heretofore in use, such as spark gaps, flares and the like, though requiring little space, have lacked the desirable heat exchange characteristics and long life necessary to effect proper ignition.

It is therefore one object of the present invention to provide an igniter which will eflect smooth and efficient ignition of a fuel-air mixture in a ram-jet engine combustion chamber.

Another object of the invention is to provide an ignition of simple and light construction, for use in a ram-jet engine.

A further object of the invention is to provide a simply constructed igniter having a widely variable rate of heat exchange and capable of sustained burning.

Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

Fig. l is a cross sectional view of the igniter according to the present invention;

Fig. 2 is a rear view of the igniter shown in Fig. 1;

Fig. 3 is a front view of the device; and

Fig. 4 is a cross section View of a ram-jet engine combustion chamber showing a cluster of igniters, constructed in accordance with the invention, mounted therein.

Broadly, the invention comprises an igniter of simple and light construction, wherein a desired igniting flame is generated by means of catalytic action on a combustible mixture containing a highly volatile fuel.

Referring now to the drawings more specifically, and to Fig. 1 in particular, the igniter comprises a flame holder 1 having a cylindrical neck section and an enlarged externally threaded body section 12. The neck section 10 has an axial bore 14 which connects a recess 17, receiving a conduit 15, and a chamber 16 that 'is States Patent O 2,970,439 Patented Feb. 7, 1961 formed in the body section 12. Chamber 16 communicates with the outer surface of the body section 12 through a plurality of orifices 18, which, as shown in Fig. 2, are arranged in a series, around the periphery of the tapered portion of body section 12. Said chamber is filled with a porous refractory material 20 composed of asbestos, silica, zirconium oxide, aluminum oxide or the like, which serves as a carrier or a support for a finely divided metallic catalyst such as platinum or palladium. Catalytic filling 20 is retained in the chamber by an axially disposed, rearwardly projecting perforated cone 22, the construction of which is also shown in Fig. 3. Cone 22 is made of a high melting point metal, such as platinum or molybdenum, and is held in place by means of an outwardly projecting annular flange 24 that is integral with its base. Flange 24 is held tightly between block 12 and a relatively thick, inwardly extending rim 26 that has a frusto-conical surface to receive the wall of said cone. Rim 26 is formed on a rearwardly extending, frusto-conical skirt 28, which serves as a flame holding baffle, and the the junction of said skirt with an internally threaded coupling sleeve 29, by which it is secured to body 12.

Referring now to Fig. 4 of the drawings, whereinis shown the preferred manner of mounting a modified igniter assembly in a combustion chamber, a plurality of igniter units 30, 32, 34 and 36 constitutes a composite igniter. Each of the units 30, 32, 34 and 36 is similar in construction to the igniter shown in Figs. 1, 2 and 3. The igniters are positioned in a cluster about the axis of the chamber by a mount 38, of strap metal. A catalytically ignitable fuel is supplied to each unit by a plurality of conduits 40, 42, 44 and 46 which have their upstream'ends mounted in couplings 48 secured to a ring 49 fitted in an annular recess in the wall of the combustion chamber, downstream from the main fuel injector 50. The couplings 48 and ring 49 serve as a fuel supply manifold for the catalytically ignitable fuel supplied to each of the igniter units. By this arrangement, proper ignition of the air-fuel mixture across the full cross sectional area of the combustion chamber can be attained. If desired, the number of igniters in the cluster can be either increased or decreased to meet the demands of the type of main fuel used, or the size of the combustion chamber.

In use, the air-fuel mixture, resulting from the injection of fuel into the chamber, flows in the direction indicated by the arrow, and a portion thereof enters the orifices 18 and permeates the catalyst bearing material 20. Hydrogen, alcohol vapor, or some similar catalytically ignitable fuel is also supplied from a source (not shown) to the chamber 16, where it reacts with the catalyst contained in the material 20, and the oxygen contained in the air-fuel mixture. The resulting reaction produces a pilot flame that is contained within the frustoconical skirt element 28, and which provides a source of ignition for the main portion of the air-fuel mixture passing through the combustion chamber, and about the igniter.

If desired, the amount of heat generated by the igniter can be controlled by regulating the flow of hydrogen to 3 teachings. It is therefore to be understood that within the scope of the'appended claims'the invention may be practiced otherwise than asspecifically described.

What is claimed is:

1. An igniter for an athodyd burner through which a combustible air-fuel mixture passes, comprising, a body mounted in the burner and having a chamber containing a porous catalyst, a plurality of bores communicating with said chamber, a central bore connecting said chamber to a source of catalytically ignitable fuel, and a plurality of orifices in the upstream end of said body through which a portion of air-fuel mixture passes into said chamber, and through the pores of the catalyst to be ignited thereby, and a frusto-conical skirt mounted on the downstream end of said body.

2. An igniter for an athodyd burner having a combustible air fuel mixture passing therethrough, said igniter comprising a body longitudinally mounted in the burner, and having a chamber in its downstream end, a perfo rated cone covering the downstream end of said chamber, a porous refractory material retained in said chamber by said cone, a metallic catalyst carried by said refractory material, bores through the body from its exterior surface and communicating with the catalyst, an additional bore in the body providing communication from a supply of catalytically ignitable gas to the catalyst, a portion of the combustible air-fuel mixture being conducted through the first-mentioned bores into the porous catalyst-bearing material and through the pores of said 'material, a catalytically ignitable gas being introduced thereto through the last-mentioned bore to mix with the air-fuel mixture and be brought in contact with the catalyst to raise its temperature and be ignited to form a pilot flame in the flame holder.

3. An igniter as set forth in claim 2, employing asbestos as the catalyst-bearing material.

4. An igniter as set forth in claim 2, employing silica as the catalyst-bearing material.

5. An igniter as set forth in claim 2, employing zirconium oxide as the catalyst-bearing material.

6. An igniter as set forth in claim 2, employing aluminum oxide as the catalyst-bearing material.

References Cited in the file of this patent UNITED STATES PATENTS 1,502,251 Kana'zawa July 22, 1924 1,753,897 Loeb Apr. 8, 1930 2,168,313 Bichowsky Aug. 8, 1939 2,385,833 Nahigyan Oct. 2, 1945 2,407,729 Taylor Sept. 17, 1946 2,433,943 Zwicky et al. Jan. 6, 1948 Skinner May 2, 1950 FOREIGN PATENTS 

